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 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package javax.script;

import java.util.List;

/**
 * <code>ScriptEngineFactory</code> is used to describe and instantiate
 * <code>ScriptEngines</code>.
 * <br><br>
 * Each class implementing <code>ScriptEngine</code> has a corresponding factory
 * that exposes metadata describing the engine class.
 * <br><br>The <code>ScriptEngineManager</code>
 * uses the service provider mechanism described in the <i>Jar File Specification</i> to obtain
 * instances of all <code>ScriptEngineFactories</code> available in
 * the current ClassLoader.
 *
 * @since 1.6
 */
public interface ScriptEngineFactory {

  /**
   * Returns the full  name of the <code>ScriptEngine</code>.  For
   * instance an implementation based on the Mozilla Rhino Javascript engine
   * might return <i>Rhino Mozilla Javascript Engine</i>.
   *
   * @return The name of the engine implementation.
   */
  public String getEngineName();

  /**
   * Returns the version of the <code>ScriptEngine</code>.
   *
   * @return The <code>ScriptEngine</code> implementation version.
   */
  public String getEngineVersion();


  /**
   * Returns an immutable list of filename extensions, which generally identify scripts
   * written in the language supported by this <code>ScriptEngine</code>.
   * The array is used by the <code>ScriptEngineManager</code> to implement its
   * <code>getEngineByExtension</code> method.
   *
   * @return The list of extensions.
   */
  public List<String> getExtensions();


  /**
   * Returns an immutable list of mimetypes, associated with scripts that
   * can be executed by the engine.  The list is used by the
   * <code>ScriptEngineManager</code> class to implement its
   * <code>getEngineByMimetype</code> method.
   *
   * @return The list of mime types.
   */
  public List<String> getMimeTypes();

  /**
   * Returns an immutable list of  short names for the <code>ScriptEngine</code>, which may be used
   * to identify the <code>ScriptEngine</code> by the <code>ScriptEngineManager</code>. For
   * instance, an implementation based on the Mozilla Rhino Javascript engine might return list
   * containing {&quot;javascript&quot;, &quot;rhino&quot;}.
   *
   * @return an immutable list of short names
   */
  public List<String> getNames();

  /**
   * Returns the name of the scripting language supported by this
   * <code>ScriptEngine</code>.
   *
   * @return The name of the supported language.
   */
  public String getLanguageName();

  /**
   * Returns the version of the scripting language supported by this
   * <code>ScriptEngine</code>.
   *
   * @return The version of the supported language.
   */
  public String getLanguageVersion();

  /**
   * Returns the value of an attribute whose meaning may be implementation-specific. Keys for which
   * the value is defined in all implementations are: <ul> <li>ScriptEngine.ENGINE</li>
   * <li>ScriptEngine.ENGINE_VERSION</li> <li>ScriptEngine.LANGUAGE</li>
   * <li>ScriptEngine.LANGUAGE_VERSION</li> <li>ScriptEngine.NAME</li> </ul> <p> The values for
   * these keys are the Strings returned by <code>getEngineName</code>,
   * <code>getEngineVersion</code>, <code>getLanguageName</code>, <code>getLanguageVersion</code>
   * for the first four keys respectively. For NAME, one of the Strings returned by
   * <code>getNames</code> is returned.<br><br> A reserved key, <code><b>THREADING</b></code>, whose
   * value describes the behavior of the engine with respect to concurrent execution of scripts and
   * maintenance of state is also defined. These values for the <code><b>THREADING</b></code> key
   * are:<br><br> <ul> <li><code>null</code> - The engine implementation is not thread safe, and
   * cannot be used to execute scripts concurrently on multiple threads.
   * <li><code>&quot;MULTITHREADED&quot;</code> - The engine implementation is internally
   * thread-safe and scripts may execute concurrently although effects of script execution on one
   * thread may be visible to scripts on other threads. <li><code>&quot;THREAD-ISOLATED&quot;</code>
   * - The implementation satisfies the requirements of &quot;MULTITHREADED&quot;, and also, the
   * engine maintains independent values for symbols in scripts executing on different threads.
   * <li><code>&quot;STATELESS&quot;</code> - The implementation satisfies the requirements of
   * <li><code>&quot;THREAD-ISOLATED&quot;</code>.  In addition, script executions do not alter the
   * mappings in the <code>Bindings</code> which is the engine scope of the
   * <code>ScriptEngine</code>.  In particular, the keys in the <code>Bindings</code> and their
   * associated values are the same before and after the execution of the script. </ul> <br><br>
   * Implementations may define implementation-specific keys.
   *
   * @param key The name of the parameter
   * @return The value for the given parameter. Returns <code>null</code> if no value is assigned to
   * the key.
   */
  public Object getParameter(String key);

  /**
   * Returns a String which can be used to invoke a method of a  Java object using the syntax
   * of the supported scripting language.  For instance, an implementation for a Javascript
   * engine might be;
   *
   * <pre>{@code
   * public String getMethodCallSyntax(String obj,
   *                                   String m, String... args) {
   *      String ret = obj;
   *      ret += "." + m + "(";
   *      for (int i = 0; i < args.length; i++) {
   *          ret += args[i];
   *          if (i < args.length - 1) {
   *              ret += ",";
   *          }
   *      }
   *      ret += ")";
   *      return ret;
   * }
   * } </pre>
   * <p>
   *
   * @param obj The name representing the object whose method is to be invoked. The name is the one
   * used to create bindings using the <code>put</code> method of <code>ScriptEngine</code>, the
   * <code>put</code> method of an <code>ENGINE_SCOPE</code> <code>Bindings</code>,or the
   * <code>setAttribute</code> method of <code>ScriptContext</code>.  The identifier used in scripts
   * may be a decorated form of the specified one.
   * @param m The name of the method to invoke.
   * @param args names of the arguments in the method call.
   * @return The String used to invoke the method in the syntax of the scripting language.
   */
  public String getMethodCallSyntax(String obj, String m, String... args);

  /**
   * Returns a String that can be used as a statement to display the specified String  using
   * the syntax of the supported scripting language.  For instance, the implementation for a Perl
   * engine might be;
   *
   * <pre><code>
   * public String getOutputStatement(String toDisplay) {
   *      return "print(" + toDisplay + ")";
   * }
   * </code></pre>
   *
   * @param toDisplay The String to be displayed by the returned statement.
   * @return The string used to display the String in the syntax of the scripting language.
   */
  public String getOutputStatement(String toDisplay);


  /**
   * Returns a valid scripting language executable program with given statements.
   * For instance an implementation for a PHP engine might be:
   *
   * <pre>{@code
   * public String getProgram(String... statements) {
   *      String retval = "<?\n";
   *      int len = statements.length;
   *      for (int i = 0; i < len; i++) {
   *          retval += statements[i] + ";\n";
   *      }
   *      return retval += "?>";
   * }
   * }</pre>
   *
   * @param statements The statements to be executed.  May be return values of calls to the
   * <code>getMethodCallSyntax</code> and <code>getOutputStatement</code> methods.
   * @return The Program
   */

  public String getProgram(String... statements);

  /**
   * Returns an instance of the <code>ScriptEngine</code> associated with this
   * <code>ScriptEngineFactory</code>. A new ScriptEngine is generally
   * returned, but implementations may pool, share or reuse engines.
   *
   * @return A new <code>ScriptEngine</code> instance.
   */
  public ScriptEngine getScriptEngine();
}
